Sorry, as there is no option to attach PDF to an email in Adobe Acrobat Reader mobile application.
However, you can share the file using the public link and then send it using your email account.
Please refer the steps provided below:
Check the screenshot below:
Please, sign-in if it prompts. Then swipe up from the bottom and click on make public.
Then select an option how you wish to share the file.
If the file is saved on device location, then you can open your email account and attach the file from that location.